This reminds me of two things. I often take my bike on a train and sometimes a heavily loaded bike can be a bit of a struggle to get on and off a train, but no one ever takes my bike to "lend a hand." Sometimes I'll deal with bike and luggage separately and then might ask another passenger if they can pass the bags to me, but if I don't ask, they won't, which is the way it should be. On one occasion I returned to Temple Meads to find the main lift out of order, so I set off up the steps. The sensible thing to do would have been to take the luggage off the bike and take it bit by bit, but... so I ground to a halt half way up the stairs.
And a nice man on the stairs, seeing my plight, did help; but spoke first. No grabbing. Which is the way it should be.
The second thing reminds me of when I lived in Warsaw, back in 2000, and worked in an office near the airport. I took the 175 bus to work, which often had airport passengers with their luggage. And gangs of thieves who would, if unsuccessful, bluster 'Oh we just wanted to help this person with their heavy luggage'. The relevance to this thread being that although most people grabbing wheelchairs or blind people's elbows are well-intentioned, a very few are intent on theft or assault and being grabbed without having been first asked activates the fear of theft or assault.